1. Field of the Invention
The present invention relates to a package structure, and more particularly to a package structure with a protecting element.
2. Description of the Prior Art
The explosive growth of high-density packaging has created a tremendous impact on the electronic assembly and manufacturing industry. Ball grid array (BGA) and chip scale package (CSP) technologies take the lead in this advanced manufacturing process. Many major equipment makers and leading electronic companies now gear up for these emerging and advanced packaging technologies.
As shown in FIG. 1A, a product of the packaging technologies, i.e. a BGA package 11 with 1.27 mm pitch (distance between adjacent ball centers of balls 113), is illustrated. The BGA package 11 is the choice for packages with higher than 300 I/Os (input/output) count, replacing leaded packages such as the quad flat pack (QFP) even for lower I/Os at present.
In the last few years, the chip size package, CSP, market has been growing very rapidly. A major benefit of the CSP package is its compact size. As shown in FIG. 1B, a CSP package 13 (a.k.a fine pitch BGA packages, FPBGAs) is illustrated. The CSP package 13 is further miniaturized version of the BGA package 11, leaded, and leadless package with pitches less than 1.27 mm. The CSP package 13 has low mass and small package size, and is generally used for low I/Os (<100) for memory and has the potential for use higher (<300) I/Os. They also provide improved electrical and thermal performance, more effective manufacturing, and ease-of-handling compared to the conventional surface mount leaded parts such as thin small outline packages (TSOPs). However, there are some issues (mainly inspection and reliability) with the implementation of the new area array packages for high reliability applications.
As shown in FIG. 1C, a CSP package consists mainly of a device 131, sealing resin 135 and solder balls 139. The solder balls 139 connect with the device 131 through a plurality of interconnecting elements 137 and a plurality of pads 141. An isolating layer 143 and the sealing resin 135 isolate the device 131 and the interconnecting elements 137. Another isolating layer 145 covers the interconnecting elements 137 to protect the interconnecting elements 137 from breaking.
The CSP package is effective for reducing the mounting area but has some reliability problems with solder joints, especially with solder joints between the interconnecting elements 137 and the pads 141. The CSP package is difficult to absorb most of the strains generated by temperature changes or impacts by deformations of its leads. Thus, as for CSP packages, strains concentrated on solder joints between the interconnecting elements 137 and the pads 141 crack the joints and consequently lower the reliability.
Thus it is necessary to develop a package structure to prevent the reliability from lowering.